TOOL 04 / FREE · NO SIGNUP
Paint Calculator
Turn net wall area into paint volume and whole containers. Keep coverage and coats visible.
Worked example loaded. These are example measurements and product assumptions.
THE METHOD
How to use this estimate
- Direct area must already exclude doors and windows. Room mode subtracts each counted opening once.
- Coverage is for one coat. The calculator applies your coat count; do not multiply coverage again.
- Container count rounds the final required volume once. Primer uses its own coverage rate and one coat.
paint litres = net paintable area × coats ÷ coverage per litre
A worked example
The “Load worked example” button uses the same inputs as this example. Explicit unit suffixes keep their meaning in either unit system.
- Input method
- Measure a rectangular room
- Length
- 12 ft
- Width / perpendicular height
- 15 ft
- Room height
- 9 ft
- Doors
- 1
- Door width
- 3 ft
- Door height
- 7 ft
- Windows
- 2
- Window width
- 4 ft
- Window height
- 5 ft
- Paint coats
- 2
- Paint coverage
- 8.589835361488905
- Waste allowance
- 0
- Paint container size
- 1 gal
- Include ceiling in room mode?
- No
- Estimate primer separately?
- No
- Paintable area
- 39.484 m² / 425 ft²
- Coats
- 2
- Containers
- 3
- Purchased paint
- 11.356 l / 3 US gal
- Estimated leftover
- 2.163 l / 0.571 US gal
Questions, answered
Why is my label different from the default coverage?
10 m²/L is a clearly marked example. Replace it with the actual product’s coverage.
Are primer and paint combined?
No. Primer is displayed separately with its own one-coat assumption.
Sources and product assumptions
These references explain units or product specifications. Your selected product label takes priority; none of these sources endorses this calculator.
- BEHR MARQUEE Interior — per-coat coverage and surface-dependent assumptions ↗
- BEHR MARQUEE No. 1450 — spread rate, coats and primer context (PDF) ↗
- NIST square-foot and US-liquid-gallon conversions ↗
- NIST US liquid gallon definition — 231 cubic inches ↗
Source check: 4 October 2026. Worked examples use stated, editable assumptions.